In my Published PCT International Patent Application PCT/US97/18351, published Apr. 18, 1998 (International Publication WO 98/16068), there is disclosed a type of camera that uses two image sensors and can produce an output of 1920.times.1080 pixels in color progressively scanned at 60 frames per second. [See, also, W. E. Glenn, and J. W. Marcinka, "1920 .times.1080 Pixel Color Camera With A Progressive Scan Output AT 60 FPS," invited paper presented at SMPTE Technical Conference, New York, N.Y., Nov. 22, 1997.] This is the "top" format in the SMPTE 274M standard. Using progressive scan rather than interlace has been a long-term objective for program production for many years. Progressive scan is widely used in computers having high definition displays. As television and computer practices converge, progressive scan display becomes more desirable. Displays such as plasma panels and light valve systems require progressive scan if they are to have full brightness and optimum motion rendition. Such displays are becoming increasingly important for high definition television.
In operation of the referenced camera system, one sensor in the camera is a color stripe filter sensor that is scanned interlaced two lines at a time to produce the color signals and low resolution luminance. Within the camera, the top octave of detail is scanned out of a second sensor at 30 frames per second. An interlaced camera also takes 1/30 second to produce the top octave of vertical detail. Both cameras produce all other spatial frequencies at 60 frames per second. Consequently, motion rendition for the referenced camera is the same as that of an interlaced camera. This was verified subjectively by comparing the two types of cameras at 525 lines where cameras were commercially available and progressively scanned at 60 frames per second. [See, W. E. Glenn, and J. W. Marcinka, "The Development Of 1080.times.1920 Pixel Color CCD Camera Progressively Scanned At 60 Frames Per Second," invited paper presented at SMPTE Technical Conference, Los Angeles, Calif., Oct. 9, 1996.]
The 1080P image derived from the referenced camera system does not have the interlace artifacts, and there is no interline flicker or line crawl. The vertical resolution is 1000 lines on a test chart, as compared with 700 lines for an interlaced camera. For a standard 1080I camera, the vertical resolution will still be 700 rather than 1000 lines. Signal scan converted from a 1080P camera or film scanned at 1080I would have the full 1000 line resolution. Because of the beneficial effect of alias frequencies produced by signals slightly above the Nyquist limit, the perceived resolution will be about 1300 lines.
In order to transmit a video signal that is within existing ATSC transmission standards, it would be desirable to have an output of the referenced camera system that is converted to interlaced format (e.g. to 1080I), and it is among the objects of the present invention to provide a camera system and method for producing such signals in interlaced format.